Overload protection arrangement for plate shears

ABSTRACT

A plate shears includes a displaceable member which is disposed in the force flow of the horizontal cutting force component occurring during a cut, the displaceable member being associated with a fracture member which fractures when the horizontal force component increases excessively and which permits the respective cutter carrier supported by the displaceable member to perform a yielding movement.

United States Patent [191 Fries et al.

[ OVERLOAD PROTECTION ARRANGEMENT FOR PLATE SHEARS [7ST inventors: eunfimiiefiai Saar; Ernst-Gunther Oberhauser, Rohrbach-Saar, both of Germany [73 A'sigii; Moeller & Neumann G.m.b.H.,

E be Lme91 [22 Filed: Feb. 24, 1972 [21] Appl.No.: 229,051

[30] Foreign Application Priority Data Feb. 26, 1971 Germany P 71 07 288.3

[52] US. Cl. 83/698, 83/543, 83/564 [51] Int. Cl 326d 7/22 [58] Field of Search 83/543, 563, 564,

[56] References Cited UNITED STATES PATENTS 2,605,836 1 8/1952 Messick 83/640 [451 Oct. 16, 1973 3,242,786 3/1966 Giordano 83/635 X FOREIGN PATENTS OR APPLICATIONS 937,634 9/1963 Great Britain 83/543 1,247,825 10/1960 France 83/640 Primary Examiner--J. M. Meister AttorneyJohn J. Dennemeyer [5 7] ABSTRACT A plate shears includes a displaceable member which is disposed in the force flow of the horizontal cutting force component occurring during a cut, the displaceable member being associated with a fracture member which fractures when the horizontal force component increases excessively and which permits the respective cutter carrier supported by the displaceable member to perform a yielding movement.

2 Claims, 4 Drawing Figures PMENIEUBU 1s m SHEET 2 UF 2 Fig. 3

OVERLOAD PROTECTION ARRANGEMENT FOR PLATE SHEARS This invention relates to an overload protection arrangement for plate shears having cutters with a horizontal cutting gap the width of which is selectively variable.

It is known that for performing clean parting cuts in particular of heavy plates, the width of horizontal cutting gap must be increased with increasing thickness of the plate to be cut. However, upon change from a large plate thickness to a smaller plate thickness the horizontal cutter gap may be accidentally omitted to be set to the width suitable for the smaller dimension. The thin plate is then not cut, but folded into the cutter gap, whereby suddenly an increased horizontal component of the cutting force is produced which in the end must be absorbed by the shear housing; normally, however, the latter is not designed for this extraordinary load, and for reasons of cost it cannot be designed to handle such a load.

Misuse can also be referred to when a plate is cropped and no account is taken of the fact that each end to be cropped has a smaller thickness than the remaining plate.

In order to avoid damage to the shears frame in spite of the ever present risk of incorrect operation of a plate shears by not selecting the correct adjustment of the horizontal cutting gap, or in order to make a particularly heavy construction of the shears frame unnecessary, the invention provides that at least one fracture member which protects the shears frame is inserted into the force flow path of the horizontal component of the cutting force which goes out from the displaceable cutter carrier and which is to be absorbed by the shears housing. This fracture member is so designed that it responds only when the horizontal component of the cutting force increases suddenly, e.g. when three times the value of the normally occurring cutting force is attained, and thus does not disadvantageously affect the rigid support of the cutter carrier on the housing in normal cutting operation.

Conventionally a fracture point is associated with a member yielding upon overload. Referred to the present invention, this yielding member is preferably a sup port element which is displaced by a rocking or pivotal movement and which ordinarily serves as a force transmitting member disposed between a cutter carrier and the shears housing. In order that such a pivotal support element, of which obviously at least two must be provided over the length ofthe displaceable cutter carrier, can be fixed in a defined position during the operation of the shears, shear pins may be used as fracture members in a construction in accordance with the invention, the shear pins being mounted in mounting blocks secured to the shears housing and engaging into the displaceable end of the support element. Instead of shear pins fracture pots according to U.S. Patent specification No. 3,] 30,613 whichare loaded purely by tension mayalternatively be utilised. 1

In a further constructional example in accordance with the invention the lower cutter carrier is connected to the shears frame by means of tie rods and is pivotally mounted at a larger spacing from its lower cutter than the tie bolts, and the tie bolts are provided with a fracture point. In this case the reaction force of the horizontal component of the cutting force exerts a torque upon the lower cutter carrier which produces increased tensional stress in the tie bolts. This opens the way for providing the tie bolts themselves, or preferably the nuts of the tie bolts, with fracture points which under overload are subjected to increased tensional stress and which in contrast to shear pins or pressure members constructed in any other manner to provide fracture points, permit a highly accurate prior calculation of the fracture load to be made. When the fracture points respond and fracture upon the shears being overloaded, the lower cutter carrier can perform a small pivotal movement whereby the load disappears which is transmitted by the upper cutter carrier and which otherwise must be absorbed by the shears frame.

Two embodiments of the invention are described below by way of example with reference to the accompanying drawings, in which:

FIG. 1 illustrates a partial vertical section through the displaceable cutter carrier in the region of a support point, 1 v I FIG. 2 illustrates a horizontal partial section on the line II II in FIG. 1,

FIG. 3 illustrates a vertical section through the lower cutter carrier and the lower part of the shears frame of a plate shears, and

FIG. 4 illustrates a detail on an enlarged scale.

A plate shears illustrated partly in FIG. 1 has a displaceable upper cutter carrier 1 with a cutter seat 2 and an upper cutter 3 which co-operates with a lower cutter 4 in a lower cutter seat 5. The horizontal component of a cutting force occurring during a cut is initially absorbed by a vertically adjustable wedge 6 which serves for adjusting the cutting gap. The adjustable wedge 6 is supported on a support element 7 which is pivotally mounted at its upper end by means of a 'pin 8 secured to the shears frame 10. The lower end of the support element 7 as may best be seen from FIG. 2 is located in a rotated position in which the said end of the support element 7 has a spacing s from the shears from 10, and is secured in this position by means of two coaxially disposed shear pins 12 and 13 which are inserted into support blocks 14 and 15 secured to the shears frame 10 and which engage in an opening 7a of the support element 7. It is understood that at least two adjusting wedges 6 with support elements 7 are provided over the length of the upper cutter carrier 1 for transmitting the horizontal component of the cutting force to the shears frame 10.

When by means of upward displacement of the adjusting wedges 6 a horizontal cutting gap has been adjusted between the cutters 3 and 4 which is found to be too large in relation to a plate thickness to be cut, this may occur e.g. when a plate is to be cropped, then the risk exists that no out is effected, but the plate is folded between the cutters 3 and 4 and clamped therebetween. In this case a horizontal component of the cutting force can be produced which is a multiple of the force for which the shears fram 10 is designed. In such event, the shear pins 12 and 13 provided with fracture points are sheared so that the lower regions of the support elements 7 are released and the elements can swing by a rocking movement towards the shears frame .through the spacing s. Thereby the shears frame 10 is prevented from being damaged.

According to FIG. 3 a lower cutter carrier 20 with its lower cutter 21 which co-operates with another cutter 23 in an upper cutter carrier 24 indicated only partly is connected to a shears frame 27 by way of tie bolts 25 and 26. Obviously more than one tie bolt 25 and one tie bolt 26 are provided over the length of the shears. The tie bolts are provided at their ends adjacent to the shears frame 27 with screw threads 25a and 26a respectively by which they are screwed into transverse pins 28 and 29, respectively, which are inserted into openings of the shears frame 27. At their free ends the tie bolts 25, 26 carry nuts 30, 31. The lower region of the lower cutter carrier 20 has bearing eyes 20a through which stationary pivot shafts 32 extend. The pivot shafts 32 are disposed at a larger spacing from the lower cutter 21 than the tie bolts 25, 26 so that the latter are subjected to increased tensional stress when a plate is being cut and a reaction force of the horizontal component of the cutting force acts upon the lower cutter 21.

In order that the connection between the lower eutter carrier 20 and the shears frame 27 can be interrupted and the lower cutter carrier 20 can pivot about the pivot shafts 32 in a direction away from the shears frame 27 when horizontal cutting force component increases suddenly owing to the horizontal cutting gap between the cutters 21 and 23 being adjusted too large, fracture points are provided in the present example in the nuts 30, 31.

For this reference is made to FIG. 4 in which an enlarged illustration of a lower tie bolt 26 with a nut 31 is given. The nut 31 is constructed as a cap nut and has a member 31c of decreased cross-section serving as fracture point between a screw threaded portion 31a and a cap member 31b. The cap member 31b is supported by means of a sleeve 33 on a wall of the lower cutter carrier 21. When a predetermined fracture load is reached the cap 31b is broken off the screw threaded portion 31a whereby the tie rod connection is interrupted.

Owing to the selected arrangement in which the tie bolts 25, 26 are located at a smaller spacing from the lower cutter carrier 21 than the pivot shaft 32, the tie rods are subjected to increased tensional stress during an overload whereby the fracture points 310 break. Since the tie bolts 25 and 26 operate under different lever conditions, the fracture points of the nuts 30 and 31 must be designed differently in respect of their predetermined fracture load. Thus, the fracture cross sections of the nuts 30 must be smaller than the fracture cross-section of the nuts 31 in order than all fracture points respond as simultaneously as possible in the case of an overload. Because in consequence of an overload the nuts 30 and 31 lose their stressing effect, the lower cutter carrier 20 can pivot away from the shears frame 27 whereby the overload is made ineffective. In order that the lower cutter carrier 20 can perform this pivotal movement, the base or foundation on which the shears rests is relieved below the lower cutter carrier 20, as may be seen at 34.

What we claim is:

1. A plate shearing means including a shears frame, upper and lower cutter means supported in upper and lower cutter carrier means mounted in said shears frame for mutually relative displacement in a vertical direction to effect a cut, wherein the lower stationary cutter carrier (20) is connected to the shears frame (27) by means of tiebolts (25,26) and pivotally mounted at a larger spacing from its lower cutter than the tie bolts, and wherein each tie bolt is provided with a fracture member (30,31).

2. A plate shearing means according to claim 1, wherein said fracture member is a nut carried by said tie bolts and provided with a fracture point (310). 

1. A plate shearing means including a shears frame, upper and lower cutter means supported in upper and lower cutter carrier means mounted in said shears frame for mutually relative displacement in a vertical direction to effect a cut, wherein the lower stationary cutter carrier (20) is connected to the shears frame (27) by means of tiebolts (25,26) and pivotally mounted at a larger spacing from its lower cutter than the tie bolts, and wherein each tie bolt is provided with a fracture member (30,31).
 2. A plate shearing means according to claim 1, wherein said fracture member is a nut carried by said tie bolts and provided with a fracture point (31c). 